Gaps are formed between the individual roll covers of conventional systems, allowing the passage of ambient air into the refrigeration unit, thus drastically lowering the energy performance of its refrigerating capacity. For this reason, according to an earlier application (Ref: PCT/EP2010/068261, corresponding to WO 2011/064318) of the same applicant, the intention was to cover the gap formed between the roll covers by using so-called intermediate roller blinds that can also be rolled up and unrolled when the roll covers are rolled up and unrolled so the resulting gap between the roll covers can be covered in the lowered position. These intermediate roller blinds and their rolling-up mechanism require a drive, so that when they are rolled up and unrolled they can always cover the gap well and at the same time ensure uniform unrolling so the fabric webs of the intermediate roller blind and the roll cover lie uniformly next to one another and thus seal well.
As mentioned in the earlier patent application, a similar device is known from DE 201 01 977 U1 that also overlaps the edges of the roll covers and can be rolled up and unrolled with them through a separate drive and a transmission gear. Since the drive of the intermediate roller blind must be synchronous with the roll covers, a suitable control of this drive is required. This driver, however, is complex and expensive, particularly because the roller blind device must be assembled on site, as the intermediate roller blind needs to engage in the roll covers so it can cover the gap by overlapping the edges. Although the earlier application resolved this deficiency, it was also relatively complex and expensive. It was also found that the proper rolling-up and unrolling of the intermediate roller blind was not always guaranteed.